Modern diesel engines include fuel systems that use a high pressure fuel pump to supply fuel to the fuel injectors. Fuel that is not used by the fuel injectors is circulated back to the fuel storage tank. Under some operating conditions, the fuel that is not used for combustion by the fuel injectors and is circulated back to the fuel storage tank may become heated during the circulation process. It is desirable to maintain the temperature of the fuel being circulated back to the fuel storage tank below a predetermined temperature. Accordingly, some vehicles are equipped with a cooling system for cooling the fuel being circulated back to the fuel storage tank.